Flame-retardant composition, preparation method and use thereof

ABSTRACT

The present invention relates to a new flame-retardant composition based on a flame retardant impregnated on an inorganic oxide of high porosity, to a process for preparing it and to its use for flame retarding materials and especially polymers.

The present invention relates to a new flame-retardant composition basedon a flame retardant impregnated on a porous support such as aninorganic oxide of high porosity, to a process for preparing it and toits use for flame-retarding materials and especially polymers.

The flame retardancy treatment of polymers is commonly carried out withflame retardants in solid form, since they are easy to incorporate intothe polymer.

Indeed the use of a liquid flame retardant necessitates the use ofpumps. This difficulty of implementation is increased still further ifthe flame retardant to be used is in the form of a viscous liquid. Inthat case it is then necessary, indeed, to provide a system for heatingthe container holding the flame retardant, the feed and discharge pipesand the pump that is used.

Moreover, the mixing of a liquid compound into a high-viscosity mediumsuch as polymers in the melted state is an elaborate operation,particularly in order to obtain homogeneous dispersion of the liquidcompound. These difficulties in implementing flame-retardant liquidcompounds have greatly limited their use, despite the promise of theirperformance and flame retardancy capacity.

The addition of flame retardant additives to the polymers is carried outeither directly, by adding the flame retardant, which is generallysolid, to the melted polymer, or by the use of mixtures in the form ofmasterbatches or concentrates. These mixtures are obtained by priormixing of a sizeable amount of the flame retardant into a matrix, whichmay be identical to the polymer to be rendered flame retardant or apolymer which allows the flame retardant to be dispersed moreeffectively. The masterbatch is shaped in the form of extruded granulesor pellets, for example. Thus the addition of red phosphorus, a compoundwhich is employed for flame retarding polyamides, is carried out viamasterbatches which are sold under the trade name Masterflam byItalmatch or Novomasse by Rhone-Poulenc.

However, the problems of dispersing the flame retardant additive in themasterbatch are still present with the liquid compounds.

Moreover, it is difficult to produce a masterbatch in compact form witha liquid flame retardant, since the principle of the compact masterbatchis to adhere fine and dusty powders to the polymer powder (PA6, forexample) by means of a substance which is fusible under the operatingconditions and which subsequently provides, by solidifying on cooling,for the integrity, non-dusting character and ready flowability of thepellets obtained.

It is also difficult to produce a milled masterbatch with a liquid flameretardant. Moreover, when the polymer selected as vehicle and the flameretardant are not miscible, mixing them leads to a two-phase dispersionwhich is very difficult to handle, for reasons of rheology, therebylimiting the flame retardant concentration of the masterbatch.

Proposals have also been made to produce polymer sponges which aresubsequently impregnated by the liquid flame retardant. These polymersponges may be obtained, for example, by injecting an inert gas such asFreon into the melted polymer, such as the Acurel products sold by Akzo.

This solution, however, is inconvenient. Moreover, the impregnationremains an elaborate operation when the flame retardant is a viscousliquid.

The need therefore exists to find a means of incorporating a liquidflame retardant, and in particular a viscous liquid flame retardant,into polymers which does not present these drawbacks.

Furthermore, certain flame retardants, especially phosphorus-based flameretardants such as phosphoric esters or phosphonic esters, may give riseto problems of stability and/or of chemical reactivity towards thepolymers into which they are introduced, depending on the introductionconditions and at the temperatures at which the polymers are shaped.

This is the case in particular with the majority of phosphoric esters orphosphonic esters, which, when they are introduced as they are intopolyamide under extrusion conditions at a temperature of between 280 and350° C., or in the course of the subsequent conversion of the mouldingpowders obtained by injection or any other process, give rise to anincrease in the viscosity index of the polyamide, which can go as far asto solidification.

Mention may be made in particular of phosphorus-based liquid flameretardants such as phosphonic acids and their esters and salts,phosphoric esters or phosphinic acids and their esters and salts.

The need exists to find a means of incorporating a flame retardant basedon phosphorus and in particular phosphoric esters or phosphonic estersinto polyamide without modification of the polyamide under theconditions of extrusion or of conversion of the products obtained.

Furthermore, certain flame retardants may give rise to problems ofexcessively low activation temperature relative to the degradationtemperature of the polymer under the effect of a flame, or else may beactive for too short a time. By activation temperature is meant thetemperature at which the flame retardancy property of the additive isdeveloped either, for example, by decomposition or by reaction with thematrix or another compound in the composition.

The need exists to find a means of modulating the activation temperatureand/or the time of action of the flame retardant.

The aim of the invention is to provide a remedy in particular for thedrawbacks indicated above, by providing a solution which allows inparticular liquid flame retardants and more particularly stillphosphorus flame retardants to be used for flame retarding polymers.

These aims and others are achieved by the present invention, whichaccordingly first provides a new flame-retardant composition comprisinga flame retardant impregnated on a porous solid support, characterizedin that that the surface of the porous support is hydrophilic orhydrophobic in nature, the organophosphorus compound having ahydrophilic or hydrophobic nature equivalent to the said surface of theporous compound.

According to one feature of the invention the liquid flame-retardantagent or compound is advantageously other than orthophosphoric acid orpolyphosphoric acid. By impregnation is meant that the flame-retardantcompound is bonded at least temporarily to the solid substrate by anytype of bonding such as absorption in the porous structure of theparticle, if such a structure exists, wetting or adsorption of theflame-retardant compound on the surface of the particles by at least onelayer of the flame-retardant compound, or fixing or grafting of theflame-retardant compound on the surface of the particles by chemical orphysico-chemical bonds.

Such adsorption or fixing is thus facilitated by the selection of asolid substrate which has surface properties which are compatible withthe properties of the flame-retardant compound. For example, a substratehaving hydrophilic surface properties is advantageously combined with aflame-retardant compound which is hydrophilic in nature, and converselyfor the compounds which are hydrophobic in nature.

Furthermore, the particle of the solid substrate may advantageouslycomprise elements and/or free radicals which promote the adsorption ofthe flame-retardant compound on the surface of the said particle.

The new flame-retardant composition of the invention has the advantageof being easy to handle and easy to incorporate into the materials whichmust be rendered fire resistant, while retaining effective flameretardancy performance.

By fire resistance is meant primarily the property of extinction and ofnon-spreading of combustion of the article. This property is illustratedin particular by standardized tests as, for example, for measuring thisproperty on moulded articles, the test called “UL94” (UnderwritersLaboratories), or, for textile articles, which is to say woven, knitted,tufted, flocked or nonwoven surfaces, tests such as that described instandard EN533, standard NF G07-128 of December 1978, standard ADB0031,published on 22 Feb. 2001, standard AITM 2.0007 B, standard AITM 2.0003or the standards NF P92.504/501/503/507, which are applicable inparticular in the construction sector.

Furthermore, this new flame-retardant composition, when based onphosphorus and in particular on phosphoric, phosphonic or phosphinicesters, can be used for flame-retarding polymers and particularlypolyamide, polyester and more generally polymers requiring a hightemperature to shape and produce articles, such as for example atemperature above 200° C. Thus, with the composition of the invention,the processes for shaping polymers may be carried out at suchtemperature levels without any substantial interaction being observed onthe properties of the polymer, such as, for example, its breakdown orsolidification. This result is of great interest, since, when such aflame retardant is introduced directly, for example into polyamide, inthe processes of extrusion or injection, an increase occurs in thedegree of polymerization of the polymer, leading to solidification,which thus prevents any utilization of a polyamide composition of thatkind. With polyesters, a degradation of the polymer preventing also theuse of these flame retardants is observed.

Moreover, this new flame-retardant composition has an activationtemperature and/or a duration of action which is adaptable to thepolymer to which it is added.

By solid substrate or porous support is meant, preferably, an inorganicsubstrate which is solid at the conversion temperature of the polymericmaterials and more particularly an inorganic oxide.

The inorganic oxide may be selected from silica, alumina,silica-alumina, sodium aluminosilicate, calcium silicate, magnesiumsilicate, zirconia, magnesium oxide, calcium oxide, cerium oxide ortitanium oxide. The inorganic oxide may be fully or partly hydroxylatedor carbonated.

Among these substrates, preference is given to those which can bedispersed in the thermoplastic material in the form of particles oraggregates of low diameter, advantageously to give dispersed particleshaving a diameter or size of less than 5 μm, and more advantageouslystill at least 80% by number of the dispersed particles have a diameteror size of less than 1 μm.

A dispersion of this kind is obtainable by mixing particles alreadyexhibiting such size characteristics into the polymeric material or,more advantageously, by using granules or agglomerates of substratesformed by the agglomeration of particles or aggregates of which at least80% have a diameter or a size of less than 1 μm. These granules oragglomerates, following addition to the polymeric material and under theaction of the shearing forces which are applied in order to produce thedispersion, break down into aggregates or elementary particles thusenabling a very good dispersion of the flame retardant in the polymer orthe polymeric material.

In this last embodiment, the agglomerates or granules preferably have ahigh specific surface area and a porosity between the importantaggregates or elementary particles, in order to allow theflame-retardant compound to be adsorbed at least on the surface of theaggregates or particles. The aggregates or particles may likewise have aporosity which allows the flame-retardant compound or agent to beabsorbed.

In this embodiment the diameter or average size of the granules oragglomerates is not critical and is advantageously selected so as toallow the flame-retardant composition to be handled readily, especiallyin the course of its addition to the polymeric material. Furthermore,the diameter or average size of these granules is likewise selected soas to facilitate the addition and adsorption of the flame-retardantcompound: for example, to prevent sticking between the various granules.

By way of indication, granules with a mean diameter D50 of more than 60μm, advantageously of between 80 μm and 300 μm, are preferred.

Among the inorganic substrates mentioned above, certain silicas exhibitthese characteristics and are therefore particularly preferred.

Thus, certain silicas, having the property of undergoing dispersion inthe form of particles or aggregates with a diameter or size of between0.005 μm and 1 μm, will be preferred for the implementation of thepresent invention.

Furthermore, the inorganic substrates which are particularly suitablefor the invention are those whose granules or agglomerates have a highporosity and a high specific surface area.

Accordingly preferred substrates are those whose granules have a totalpore volume of at least 0.5 ml/g, preferably at least 2 ml/g. This porevolume is measured by the mercury porosimetry method using aMicromeritics Autopore III 9420 porosimeter, in accordance with thefollowing technique:

The sample is dried for 2 hours in an oven at 200° C. beforehand. Themeasurements are subsequently carried out in accordance with theprocedure described in the manual supplied by the manufacturer.

The pore diameters or pore sizes are calculated by means of the Washburnequation with a contact angle equal to 140° and a surface tension gammaof 485 dynes/cm.

Advantageously, the inorganic substrates or porous supports which have apore volume of at least 0.50 ml/g for pores whose diameter or size isless than or equal to 1 μm are preferred.

According to one preferred embodiment of the invention the inorganicsubstrate is a silica, advantageously an amorphous silica. Silicas areobtained by various processes, including two main processes which leadto silicas referred to as precipitated silica and fumed silica. Silicamay also be prepared in gel form.

Silicas having a specific surface area, measured in accordance with theCTAB method, of greater than 50 m²/g are preferred.

Precipitated silicas are preferred because they may be in the form ofagglomerated particles forming granules with a size of at least 50 μm orgreater than 150 μm.

They may be in the form of beads or granules which are substantiallyspherical, obtained for example by spraying, as described in EuropeanPatent No. 0018866. This silica is sold under a generic name ofMicropearl. Silicas of this kind having significant properties offlowability, dispersibility and a high impregnation capacity aredescribed in particular in European Patents 966207, 984773 and 520862and in international applications WO95/09187 and WO95/09128.

Other types of silica may be suitable for the invention, such as thosedescribed in French Patent Application No. 01 16881, which are pyrogenicsilicas, or silicas partially dehydroxylated by calcining or surfacetreatment.

These examples of silicas used as solid inorganic substrate aredescribed only by way of indication and as preferred embodiments. It isalso possible to use other silicas obtained by other processes andhaving porosity and dispersibility properties which are suitable forperforming the invention.

According to the invention the flame retardant additive comprises aflame-retardant compound which is adsorbed on inorganic substrateparticles. In one preferred embodiment of the invention this adsorptionis obtained by impregnating granules or agglomerates. This impregnationis carried out by any conventional means and, for example, by mixing thesubstrate with the flame-retardant compound in the liquid state or in aform in which it is dispersed or in solution in a solvent. In thislatter case the solvent will be removed, following impregnation of thesubstrate, by evaporation.

The term “flame retardant” or “flame-retardant compound” should beunderstood to refer to one or more flame-retardant compounds, or to amixture of compounds forming a system which has flame retardancyproperties.

The inorganic oxide is preferably precipitated silica, and may forexample be a silica which is sold under the trade names Tixosil 38A,Tixosil 38D or Tixosil 365 by Rhodia.

The precipitated silica may be a highly dispersible silica, such as thesilicas described in EP 520862, WO 95/09127 or WO 95/09128, therebyfacilitating its dispersion in the polymer and having a positive effecton the mechanical properties of the material obtained. The silica inquestion may be, for example, a silica which is sold under the tradenames Z1165 MP or Z1115 MP by Rhodia.

In particular the precipitated silica may be in the form ofsubstantially spherical beads with an average size in particular of atleast 80 microns, for example of at least 150 microns, which areobtained by means of a nozzle sprayer, as described for example in EP0018866. The silica in question may be, for example, silica calledMicropearl. This form allows the impregnation capacity and flowabilityof the powder to be optimized, as described for example in EP 966207 orEP 984772. The silica in question may be, for example, a Tixosil 38X orTixosil 68 silica from Rhodia.

This makes it possible to use a gravimetric powder metering apparatus inorder to introduce the resultant flame retardant powder, since thispowder flows well and does not dust.

The amorphous silica may be a silica featuring low water regain. “Waterregain” which corresponds to the quantity of water integrated into thesample, relative to the mass of the sample in the dry state, after 24hours at 20° C. and 70% relative humidity. Low water regain refers to awater regain of less than 6% and preferably of less than 3%. The silicasin question may be precipitated silicas described in patent applicationFR 01 16881, filed on 26 Dec. 2001 by Rhodia, pyrogenic silicas orsilicas partially dehydroxylated by calcining or by surface treatment.

The flame retardant of the invention is advantageously liquid at ambienttemperature (approximately 25° C.). This liquid flame retardant may beselected from all of the liquid flame retardants which are known to theperson skilled in the art, with the exception of orthophosphoric acid orof polyphosphoric acid.

Mention may be made in particular of liquid flame retardants based onphosphorus, such as phosphonic acids and their esters and salts,phosphoric esters or phosphinic acids and their esters and salts.

Use may be made in particular of liquid flame retardants which areviscous, which stick and/or which are difficult to handle or to clean.

A viscous liquid is any liquid which has a viscosity of more than 100centipoises at a temperature of 25° C., preferably more than 1000centipoises at a temperature of 25° C., and more preferably still morethan 10000 centipoises at a temperature of 25° C., this viscosity beingmeasured by a Brookfield-type apparatus with a spindle and a rotationalspeed which is adapted to the viscosity measured. For example,cylindrical spindle and a rotational speed of 50 rpm are used where theviscosity is in the region of 100 centipoises.

As flame-retardant compounds which are suitable for the inventionmention may be made by way of example ofmethylbis(5-ethyl-2-methyl-2-oxido-1,2,3-dioxaphosphorinan-5-yl)methylphosphonicacid, alone or in a mixture withmethyl(5-ethyl-2-methyl-2-oxido-1,3,2-dioxaphosphorinan-5-yl)methylphosphonicacid, resorcinol bis(diphenyl phosphate), bisphenol A bis(diphenylphosphate), polyphosphate esters diethylphosphinic acid,ethylmethylphosphinic acid, methyl-n-propyl-phosphinic acid andmixtures, esters and salts thereof.

By way of illustration mention may be made of viscous liquids sold underthe trade names Antiblaze 1045 (mixture ofmethylbis(5-ethyl-2-methyl-1,3,2-dioxaphosphorine)phosphonic acid andmethyl(5-ethyl-2-methyl-2-oxido-1,3,2-dioxaphospho)phosphonic acid),which is sold by Rhodia and whose viscosity as indicated on the datasheets is 500 000 centipoises at 25° C. and 1000 centipoises at 110° C.;Fyrolflex RDP (resorcinol bis(diphenyl phosphate)), which is sold byAkzo and whose viscosity as indicated on the data sheets is 600centipoises at 25° C.; and Fyrolflex BDP (bisphenol A bis(diphenylphosphate)), which is sold by Akzo and whose viscosity as indicated onthe data sheets is 12450 centipoises at 25° C.

By way of illustration mention may also be made of the compounds orcompositions which are sold by Rhodia under the trade name Antiblaze CUor Antiblaze CT, which have a viscosity as indicated on the data sheetsof 500 000 centipoises at 25° C. and 1000 centipoises at 110° C. andwhich contain the products present in Antiblaze 1045 in differentproportions, the diphenyl phosphate ester derivatives sold by Akzo underthe name Fyrolflex, whose viscosity as indicated on the data sheets is12450 centipoises at 25° C., or by Great Lakes Chemical Corp. under thename Rheophos DP. Finally, Daihachi Chemical Industry sellspolyphosphate esters under the names CR 741, CR 733 and CR 741S.

As indicated above, these compounds may be impregnated directly on thesubstrate, such as a silica for example, or may be dissolved in asolvent such as, for example, water, organic solvents such as ketones,alcohols, ethers, hydrocarbons, and halogenated solvents, for example.

It is preferred to use a liquid flame retardant. It may, however, bepreferred, in order for example to avoid hot impregnation, to dissolvethe flame retardant in a solvent. The solid substrate is thenimpregnated with the solution obtained. In this case it is possible toremove the solvent by drying.

Impregnation is preferably carried out dry; that is, the flame-retardantcompound is added gradually to the solid substrate in order to allowtotal impregnation or adsorption. For that purpose it is necessary forthe flame-retardant compound or the solution of the flame-retardantcompound to have a sufficient fluidity. Thus in order to obtain thisfluidity level the said impregnation or adsorption can be carried out attemperatures higher than the ambient temperature, within a range ofbetween 20° C. and 200° C., preferably less than 100° C.

The solid substrate may also be preheated in the same temperature rangein order to facilitate impregnation, particularly if the product needsto be fluidized by heating. The porous support or solid substrate mayalso be dried before impregnation, either by drying or by calcining, inorder to remove the water present. This makes it possible to adapt thehydrophilic or hydrophobic nature of the surface of the porous supportdepending on the flame-retardant product to be impregnated.

Drying may be carried out by any of the conventional techniques known tothe person skilled in the art.

Impregnation may take place in a single step or in two or moresuccessive steps.

The amount of flame retardant impregnated or adsorbed may vary withinlarge proportions. However, it is limited and at most equal to theamount necessary to fill the total pore volume of the inorganicsubstrate in the case where granules or agglomerates which exhibitporosity are impregnated. This is because the flame retardant additivewhich must be added to the polymeric material must preferably be apowder or a solid in the form of granules which exhibit good fluidity inorder to allow this addition. In the case where particles or aggregatesare impregnated the amount of flame-retardant compound added isdetermined so as to give an impregnated solid product which can behandled and added to the polymeric material. The concentration by weightof flame-retardant compound in the flame retardant composition ispreferably between 20% and 70% relative to the weight of flame retardantcomposition, advantageously between 20% and 50%.

If the flame retardant is too viscous at ambient temperature to beimpregnated it may be heated beforehand and hence the impregnation maybe carried out hot.

The temperature range used for hot impregnation is between 30 and 300°C. The temperature used for hot impregnation is preferably between 50and 100° C.

The inorganic oxide may also be preheated in the same temperature rangein order to facilitate impregnation.

It is preferred to use a concentrated liquid flame retardant. It may bepreferable, however, in order to avoid hot impregnation for example, todilute the flame retardant in a solvent. In that case the inorganicoxide is impregnated with the solution obtained. It is possible in thiscase to remove the solvent from the impregnated inorganic oxide bydrying.

Impregnation may take place in a single step or in two or moresuccessive steps of impregnation.

The flame retardant additive may be present in the form of a powder,which can be shaped in accordance with the shaping methods commonlyemployed in industry.

The present invention further provides for the use of theabove-described flame-retardant composition for flame retarding variousmaterials, especially polymers, such as thermoplastic polymers,thermosetting polymers and elastomers.

When the polymer or copolymer is thermoplastic it may be a polymerselected from polyamides, polycarbonates, polyesters, styrenic polymers,acrylic polymers, polyolefins, polyvinyl chlorides and derivativesthereof, polyphenyl ethers, polyurethanes or mixtures thereof.

When the polymer is a thermoplastic or thermosetting polyamide it isselected from the group consisting of polyamides obtained bypolycondensation of a linear dicarboxylic acid with a linear or cyclicdiamine, such as PA 6.6, PA 6.10, PA 6.12, PA 12.12, PA 4.6, MXD 6, orof an aromatic dicarboxylic acid and a linear or aromatic diamine, suchas polyterephthalamides, polyisophthalamides, polyaramides, polyamidesobtained by polycondensation of an amino acid with itself, it beingpossible for the amino acid to be generated by the hydrolytic opening ofa lactam ring, such as, for example PA 6, PA 7, PA 11, PA 12. It is alsopossible to use copolyamides derived in particular from the abovepolyamides, or mixtures of these polyamides or copolyamides.

Branched polyamides and star polyamides can also be used.

Preferred polyamides are polyhexamethyleneadipamide, polycaprolactam, orcopolymers and mixtures of polyhexamethyleneadipamide withpolycaprolactam.

When the polymer is a polyester it may be, for example, polybutyleneterephthalate, polypropylene terephthalate or polyethylene terephthalateor mixtures thereof.

When the polymer is a styrenic polymer it may be, for example,polystyrene, styrene-butadiene (SB), polystyrene-acrylonitrile (SAN),acrylonitrile-butadiene-styrene (ABS), or copolymers thereof or mixturesthereof.

When the polymer or copolymer is a polyolefin it may be selected forexample from polypropylene, polyethylene, ethylene/vinyl acetate (EVA)copolymer or mixtures thereof.

When the polymer is thermosetting it may be a polymer selected frompolyurethane, epoxy resins (such as Araldite), polyester resins,phenolic resins (such as Bakelite) or amino resins (such as Formica).

When the flame-retardant composition of the invention is added tothermoplastic polymers (including thermoplastic elastomers) it isincorporated by mixing, preferably in a single-screw or twin-screwextruder. The mixture is extruded in the form of articles such asprofiles or, more advantageously, in the form of strands which will becut into granules. The granules are used in processes for producingarticles, as a raw material, and will be melted in order to supply theflame-retarded composition in shaping processes such as processes ofmoulding by injection, extrusion, extrusion blow moulding or the like.

The mixture may further comprise one or more additives which arecommonly employed in this field.

The total amount of flame-retardant composition according to theinvention that is used varies between 1 to 50% relative to the totalweight of the mixture obtained. The total amount of flame-retardantcomposition is preferably between 10 to 40% relative to the total weightof the mixture obtained. More preferably still the total amount offlame-retardant composition is between 15 to 30% relative to the totalweight of the mixture obtained.

When the inorganic oxide impregnated with liquid flame retardant isincorporated into thermosetting polymers the inorganic oxide impregnatedwith liquid flame retardant and the other additives are incorporatedinto one of the monomers or oligomers before the polymerization orcrosslinking reaction. The amounts of inorganic oxide impregnated withliquid flame retardant that are used are in the same proportions asthose described for the thermoplastic polymers.

It is possible additionally to add all of the additives which aregenerally employed for the production of compositions which are used,for example, for manufacturing moulded articles in particular in theelectrical field.

By way of example mention may be made of fillers, including reinforcingfillers, heat or light stabilizer additives, additives which enhanceimpact resistance, pigments and dyes. This list is not at all limitativein nature.

Other aspects and advantages of the products which are the subject ofthe invention will emerge on reading the examples given below by way ofillustration and in no way limitative.

A-Preparation Examples of a Highly Porous Silica Impregnated with aConcentrated Liquid Flame Retardant According to the Invention EXAMPLE 1Preparation of a Highly Porous Silica Impregnated with Antiblaze 1045

The highly porous silica used is a silica called Tixosil 38A fromRhodia, having a total pore volume of 4.2 ml/g and a useful volume of2.2 ml/g.

The amount of concentrated Antiblaze used for impregnation correspondsto the maximum amount which can be impregnated onto the silica, in otherwords the volume for which saturation of the silica is obtained.Impregnation takes place dry. Antiblaze 1045, heated to 80° C.beforehand in order to make it more fluid, is added dropwise from aburette in portions of 25 ml.

25 grams of silica are weighed out. The maximum impregnated volumeattained is 50 ml of Antiblaze 1045, equivalent to 63 g.

The end product is therefore composed of 71.6% by weight of Antiblaze1045 and 28.4% of silica.

The product is in the form of a powder whose diameter (D50) from theparticle size distribution is 250 μm (D50, in the field of powdergranulometry, is the particle diameter or size for which 50% by weightof the particles have a lower diameter and 50% by weight have a higherdiameter).

The phosphorus content of this powder is 15%.

EXAMPLE 2 Preparation of a Highly Porous Silica Impregnated withAntiblaze 1045

The highly porous silica used is a silica called Tixosil 38X from Rhodiawhich has a total pore volume of 3.6 ml/g and a useful pore volume of2.0 ml/g. It is a silica called Micropearl which possesses excellentflowability and does not dust.

3.5 kg of silica are weighed out and introduced into a jacketed 20-litreLödige mixer. The silica is heated to 95° C. (the setpoint temperatureof the thermostatic bath is 135° C.).

Beforehand, Antiblaze 1045 was placed in an oven at 80° C. overnight. Itis subsequently pumped into a jacketed feed vessel thermostated at 99°C. and is introduced into the Lödige without spraying (introduction flowrate: 45 min at 4.1 l/h and 1 h 30 min at 1.9 l/h).

The rotational speed of the ploughshare in the Lödige is 70 rpm.

The total amount of Antiblaze 1045 introduced into the silica is 6.696kg (equivalent to 5314 ml).

The end product is subsequently screened on a 1.25 mm sieve.

The end product is therefore composed of 65.6% by weight of Antiblaze1045 and 34.4% of silica.

It is in the form of a powder which possesses excellent flowability,similar to that of the initial Micropearl silica Tixosil 38X, with nodusting by the product, whose diameter (D50) from the particle sizedistribution is 250 μm.

The phosphorus content of this powder is 13.6%.

EXAMPLE 3 Preparation of a Highly Porous Silica Impregnated withFyrolflex RDP

The highly porous silica used is a silica called Tixosil 38A fromRhodia, having a total pore volume of 4.2 ml/g and a useful pore volumeof 2.2 ml/g.

The amount of concentrated Fyrolflex RDP used for impregnationcorresponds to the maximum amount which can be impregnated onto thesilica, in other words the volume for which saturation of the silica isobtained. Impregnation takes place dry. Fyrolflex RDP, which is atambient temperature is added dropwise from a burette in portions of 25ml.

25 grams of silica are weighed out. The maximum impregnated volumeattained is 50 ml of Fyrolflex RDP, equivalent to 65 g.

The end product is therefore composed of 72.2% by weight of FyrolflexRDP and 27.8% of silica.

The product is in the form of a powder whose diameter (D50) from theparticle size distribution is 60 μm. The powder thus obtained has aparticle size which is much lower than the Tixosil 38A silica startingproduct. The impregnation with Fyrolflex RDP therefore leads to a powderwhich has poorer dusting and flowability properties than thenon-impregnated silica.

The phosphorus content of this powder is 7.6%.

EXAMPLE 4 Preparation of a Highly Porous Silica Impregnated withAntiblaze CU

The highly porous silica used is a silica called Tixosil 38X from Rhodiawhich has a total pore volume of 3.6 ml/g and a useful pore volume of2.0 ml/g. It is a silica called Micropearl which possesses excellentflowability and does not dust.

3.5 kg of silica are weighed out and introduced into a jacketed 20-litreLödige mixer. The silica is heated to 95° C. (the setpoint temperatureof the thermostatic bath is 135° C.).

Beforehand, Antiblaze CU was placed in an oven at 80° C. overnight. Itis subsequently pumped into a jacketed feed vessel thermostated at 99°C. and is introduced into the Lödige without spraying (introduction flowrate: 45 min at 4.1 l/h and 1 h 30 min at 1.9 l/h).

The rotational speed of the ploughshare in the Lödige is 70 rpm.

The total amount of Antiblaze CU introduced into the silica is 6.696 kg(equivalent to 5314 ml).

The end product is subsequently screened on a 1.25 mm sieve.

The end product is therefore composed of 65.6% by weight of Antiblaze CUand 34.4% of silica.

It is in the form of a powder which possesses excellent flowability,similar to that of the initial Micropearl silica Tixosil 38X, with nodusting by the product, whose diameter (D50) from the particle sizedistribution is 250 μm.

The phosphorus content of this powder is 13.5%.

B-Preparation of Flame-Retardant Polymeric Compositions

B-1 Polyamide

The flame-retardant products obtained in Example 1 and in Example 2 areincorporated into a polymeric matrix of polyamide 6 and polyamide 66 inmelted medium with the aid of a single-screw or twin-screw extruder. Themixture is extruded generally in the form of strands which are cut inorder to give granules.

These granules are used as raw material for supplying processes formanufacturing flame-retarded moulded articles by injection, moulding,extrusion blow moulding or by any other process for shaping articles.

The properties of these compositions are measured on the basis of testspecimens obtained by injection moulding a polyamide compositionadditized with the powder of Example 2 in accordance with the proceduredescribed below:

B-1-1 Preparation of Flame-Retarded Polyamide 6 (PA6) Test Specimens

Preparation of Granules

A polyamide 6 composition containing 20% of glass fibres is extruded ina Leistritz twin-screw extruder with a flow rate of between 6 and 7kg/hour, imposing a temperature profile of 250° C. on average and apressure in the degassing zone of approximately 400 mbar. The meltpressure measured at the die is in the region of 8 bar.

The product obtained at the end of the preparation described in Example2 is added with the aid of a gravimetric powder metering apparatus at arate which is determined so as to give a proportion of product in thepolymer of 20% by weight relative to the end composition. The strandsobtained are cut into granules.

The good flowability of the powder allows standard metering systems tobe used without any difficulty and in particular without dusting.

Preparation of Test Specimens

The test specimens are obtained by injection moulding the granulesobtained above under standard conditions on an 85-tonne Billon presswith a cycle time of 40 seconds, a mould temperature of 80° C. and atemperature profile imposed on the sleeve of 250° C. The test specimensobtained are of standardized shape for the implementation of the UL-94test for determining flame retardancy properties. Test specimens with athickness of 1.6 mm and 0.8 mm were produced.

B-1-2 Preparation of Additized Polyamide 66 (PA66) Test Specimens

Preparation of Granules

A polyamide 66 composition containing 20% of glass fibres is extruded ina Leistritz twin-screw extruder with a flow rate of between 6 and 7kg/hour, imposing a temperature profile in the screw of 280° C. onaverage and a pressure in the degassing zone of approximately 400 mbar.The melt pressure measured at the die is in the region of 8 bar.

In a first experiment the product of Example 2 and in a secondexperiment the product of Example 4 are added with the aid of agravimetric powder metering apparatus at a rate which is determined soas to give a proportion of product in the polymer of 20% by weightrelative to the end composition.

The good flowability of the powder allows standard metering systems tobe used without any difficulty and in particular without dusting.

The strand obtained is cut into granules in a customary fashion.

Preparation of Test Specimens

The test specimens are obtained by injection moulding the granulesobtained above under standard conditions on an 85-tonne Billon presswith a cycle time of 40 seconds, a mould temperature of 80° C. and atemperature profile imposed on the sleeve of 280° C. so as to give testspecimens with a thickness of 1.6 mm and 0.8 mm with a form which isstandardized for carrying out the UL-94 test.

B-1-3 Preparation of Additized Polyamide 66 (PA66) Test Specimens

Preparation of Granules

A polyamide 66 composition containing 20% of glass fibres is extruded ina Leistritz twin-screw extruder with a flow rate of between 6 and 7kg/hour, imposing a temperature profile in the screw of 280° C. onaverage and a pressure in the degassing zone of approximately 400 mbar.The melt pressure measured at the die is in the region of 8 bar.

The product of Example 3 is added with the aid of a gravimetric powdermetering apparatus at a rate which is determined so as to give aproportion of product in the polymer of 20% by weight relative to theend composition.

The good flowability of the powder allows standard metering systems tobe used without any difficulty and in particular without dusting.

The strand obtained is cut into granules in a customary fashion.

Preparation of Test Specimens

The test specimens are obtained by injection moulding the granulesobtained above under standard conditions on an 85-tonne Billon presswith a cycle time of 40 seconds, a mould temperature of 80° C. and atemperature profile imposed on the sleeve of 280° C. so as to give testspecimens with a thickness of 1.6 mm and 0.8 mm. This injection mouldingwas not carried out properly because the injection screw became blocked.The reason for this blockage may be a problem of plastification of thePolyamide which may be due to low affinity between the Fyrolflex RDP,which has a hydrophobic character, and the silica, which has a surfacewith a hydrophilic character.

2) Determination of the Fire Behaviour of the Polyamide Test Specimens

The fire behaviour of the samples obtained above is determined accordingto the UL-94 test written by Underwriters Laboratories and described inStandard ISO 1210:1992(F). This test is carried out with test specimenshaving a thickness of 1.6 mm and 0.8 mm.

The results obtained for the test specimens obtained above are collatedin table I below. Before the UL-94 test is carried out the testspecimens are conditioned by keeping them in an atmosphere having arelative degree of humidity of 50% at 23° C. for 48 hours. TABLE IConditioning Classification Test specimen thickness (mm) 1.6 0.8 PA6620% GF V2 NC PA66 20% GF + 20% product of Example 2 V0 V1 PA66 20% GF +20% product of Example 4 V0 V0 PA63 20% GF NC NC PA63 20% GF + 20%product of Example 2 V2 V2GF signifies glass fibre

These tests show that the product obtained at the end of the preparationdescribed in Example 2 imparts satisfactory flame retardance propertiesto the polyamide. A V0 classification in fact is obtained for athickness of 1.6 mm for the polyamide 66, and flame retardancyperformances are obtained which are substantially improved for thepolyamide 6 by comparison with the same polyamide 6 tested without thisadditive.

The compositions flame retarded with the powder of Example 3 were nottested, since it was impossible to produce proper test specimens.

B-2 Polypropylene

1) Preparation of Polypropylene (PP) Test Specimens

Two Formulas are Prepared:

Formula 1:

Polypropylene alone is ground at 200 rpm for 3 minutes at 155° C.

Subsequently 18% by weight of the powder corresponding to Example 1,relative to the total weight of the mixture, 6% by weight ofpentaerythritol relative to the total weight of the mixture and 6% byweight of melamine relative to the total weight of the mixture areintroduced into the mixer and grinding is continued for 3 minutes.

Formula 2:

Polypropylene alone is ground at 200 rpm for 3 minutes at 155° C.Subsequently 20% by weight of the powder corresponding to Example 1,relative to the total weight of the mixture, is introduced into themixer and grinding is continued for 3 minutes.

These formulas are then moulded by thermal compression at a temperatureof 190° C. at 1 bar for 4 minutes and then at 100 bars for 1 minute andat 200 bars for 1 minute, followed by cooling for 4 minutes, duringwhich this pressure of 200 bars is maintained.

Using the appropriate moulds, this thermal compression process givesbars for the fire behaviour tests of type UL-94 (thickness: 3.2 mm).

2) Determination of the Fire Behaviour of the Test Specimens

The fire behaviour of the samples obtained with the two formulas isdetermined in accordance with the UL-94 test according to theUnderwriters Laboratories procedure described in Standard ISO 1210:1992(F).

The results obtained with the bars containing formulas 1 and 2 arecollated in table II below. TABLE II Thickness of UL samples (mm) 3.2 PPalone NC Formula 1 V2 Formula 2 V2

These tests show that the product corresponding to Example 1 impartssatisfactory combustion properties to polypropylene, particularly whenthis product is introduced alone into polypropylene (formula 2), since aV2 classification is obtained (NC for polypropylene alone) for a levelof additive of 20%.

The addition of pentaerythritol and of melamine in addition to theproduct corresponding to Example 1 to the polypropylene (formula 1)gives a classification which remains correct (V2 as against NC forpolypropylene alone) but at a higher overall level of additives.

The advantage of the product corresponding to Example 1 as a flameretardant which significantly enhances the fire retardancy performanceof polypropylene is therefore evident.

1-30. (canceled)
 31. A flame-retardant composition comprising a flameretardant organophosphorus compound impregnated on a porous solidsupport presenting an hydrophilic or hydrophobic surface, theorganophosphorus compound having a hydrophilic or hydrophobic naturesimilar to said surface of the porous compound.
 32. The compositionaccording to claim 31, wherein the porous support is an inorganic oxidehaving a total pore volume of at least 0.5 ml/g.
 33. The compositionaccording to claim 32, wherein the inorganic oxide is an inorganic oxidehaving a total pore volume of at least 2 ml/g.
 34. The compositionaccording to claim 31, wherein the inorganic oxide is silica, alumina,silica-alumina, sodium aluminosilicate, calcium silicate, magnesiumsilicate, zirconia, magnesium oxide, calcium oxide, cerium oxide ortitanium oxide.
 35. The composition according to claim 31, being inpowder form composed of porous granules or agglomerates having a meandiameter (D50) of greater than or equal to 60 μm.
 36. The compositionaccording to claim 35, wherein the granules or agglomerates are composedof an agglomeration particles or aggregates of which at least 80% bynumber have a size of less than 1 μm.
 37. The composition according toclaim 35, wherein the granules or agglomerates have a porosity of atleast 0.5 ml/100 g.
 38. The composition according to claim 34, whereinthe inorganic oxide is a silica.
 39. The composition according to claim38, wherein the silica is an amorphous silica.
 40. The compositionaccording to claim 39, wherein the amorphous silica is a syntheticsilica.
 41. The composition according to claim 40, wherein the syntheticsilica is a precipitated silica.
 42. The composition according to claim40, wherein the precipitated silica is in the form of substantiallyspherical beads with a mean diameter (D50) of at least 80 μm.
 43. Thecomposition according to claim 42, wherein the mean diameter (D50) is ofat least 150 microns.
 44. The composition according to claim 38, whereinthe silica is a highly dispersible silica.
 45. The composition accordingto claim 31, wherein the organophosphorus compound is liquid at ambienttemperature.
 46. The composition according to claim 31, wherein theorganophosphorus compound is an phosphonic acid, a salt thereof, anester thereof, a phosphoric ester, a phosphinic acid, a salt thereof oran ester thereof.
 47. The composition according to claim 46, wherein thethe organophosphorus compound ismethylbis(5-ethyl-2-methyl-2-oxido-1,2,3-dioxaphosphorinan-5-yl)methylphosphonicacid, a mixture ofmethylbis(5-ethyl-2-methyl-2-oxido-1,2,3-dioxaphosphorinan-5-yl)methylphosphonicacid with methyl(5-ethyl-2-methyl-2-oxido-1,3,2-dioxaphosphorinan-5-yl)methylphosphonicacid, resorcinol bis(diphenyl phosphate), bisphenol A bis(diphenylphosphate), polyphosphate esters diethyl-phosphinic acid,ethylmethyl-phosphinic acid, methyl-n-propyl-phosphinic acid, an esterthereof or a salt thereof.
 48. The composition according to claim 31,wherein the flame retardant has a weight concentration of between 20 and70% relative to the weight of the composition.
 49. A process forproducing a composition having flame retardancy properties as defined inclaim 31, comprising the step of impregnating the flame retardant on theporous support by a dry impregnation.
 50. The process according to claim49, wherein the flame retardant is a viscous liquid.
 51. The processaccording to claim 50, wherein the viscosity of the flame retardant isgreater than or equal to 100 centipoises at 25° C.
 52. The processaccording to claim 51, wherein the viscosity of the flame retardant isgreater than or equal to 1000 centipoises at 25° C.
 53. The processaccording to claim 52, wherein the viscosity of the flame retardant isgreater than or equal to 10000 centipoises at 25° C.
 54. A process forcarrying out a flame retardancy treatment on polymers, comprising thestep of incorporating by mixing a composition as defined in claim 31 insaid polymers.
 55. The process according to claim 54, wherein thepolymers are thermosetting polymers, thermoplastic polymers orelastomers.
 56. The process according to claim 54, wherein thethermoplastic polymer are polyolefins, polyamides or polyesters.
 57. Theprocess according to claim 56 wherein the polyolefin is polypropylene.58. The process according to claim 56, wherein the polymer is polyamide6, polyamide 66, branched polyamides, star polyamides, polyamide 12,polyamide 11 or a mixture thereof.